Frangible tension shock absorber

ABSTRACT

A tension shock absorber comprises a length of music wire, one end of which is passed through a hole in an anvil the diameter of which conforms closely to the diameter of the wire. The portion of the wire which has not passed through the anvil is plated with a frangible metal. Excessive tension forces applied to the unplated end of the wire cause the anvil to peel the plating from the wire. A fixed sleeve closely surrounding the plated portion of the wire a short distance from the face of the anvil prevents premature propagation of peeling.

I United States Patent 51 3,670,852

Yarm 1 June 20, 1972 FRANGIBLE TENSION SHOCK 3,398,812 8/l968 Peterson..l88/1 C ABSORBER Primary Examiner-Duane A. Reger [72] Inventor: JayYam, AuomeyMaurice B. Tasker and Vernon F hauschild [73] Assignee:United Aircraft Corporation, East Hartford, Conn. [57] ABSTRACT Atension shock absorber com rises a len th of music wir l b. 97 P 8 [22]F1 ed Fe l 1 one end of which is passed through a hole in an anvil the[2]] Appl. No.: 116,323 diameter of which conforms closely to thediameter of the wire. The portion of the wire which has not passedthrough the anvil is plated with a frangible metal. Excessive tensionforces [52] 74/492 applied to the unplated end of the wire cause theanvil to peel [51] Int. Cl ..Fl6f 7/12 the plating f the wire. A fixedsleeve closely surrounding [5 8] Field of Search ..74/492, 493; 188/! Cplated portion of the i a Short dismnce from he face of the anvilprevents premature propagation of peeling. [56] References Cited 16Claims, 5 Drawing Figures UNITED STATES PATENTS 2,682,931 7/1954 Young..l83/l C l i Zfl I I II I w PATENTEDJUHO 1:72

'Flcs2 FIGJ FRANGIBLE TENSION SHOCK ABSORBER CROSS-REFERENCE TO RELATEDAPPLICATIONS An application of Jay M. Yarm and Edmond F. Kelly, Ser. No.879,666, filed Nov. 25, 1969 and assigned to the assignee of the presentapplication, discloses a wire or rod member having a plated-on retentionmeans which is enclosed in a counterbore to prevent stripping. Thisapplication contains information pertinent to the practice of thepresent invention and reference is made thereto as supplementing thedisclosure of this application.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to a tension shock absorber utilizing a length of plated wireand an anvil for stripping the plating from the wire. One use for thisdevice, for example, is in connection with cables used for stoppingaircraft as they land on a carrier deck. It is also well suited for usewith automobile and aircraft seat restraints where a shock absorber freefrom elastic rebound is of utmost importance.

2. Description of the Prior Art Frangible materials such as balsa andhoneycomb or tubing forced over an anvil have been used where extremeenergy absorption by compression is desired for a one-time use. Tensionshock absorbers utilizing the principle of material deformation havealso been used. U.S. Pat. No. 2,682,931, issued July 6, 1954 to V. M.Young shows a malleable rod which is deformed by being drawn through adiameter reducing die to provide such a non-elastic energy absorbingdevice. U. S. Pat. No. 3,026,972, issued Mar. 27, 1962 to G. I-Iendry etal. shows a metal tube of circular cross-section and a mandrel ofgenerally square cross-section located at one end of the tube which isdrawn through the tube and deforms it to provide similar energydissipation.

Others have proposed energy absorbers by plastic deformation (materialdeformed beyond yield point) of steel members in tension. All of thesedevices have been difficult to produce and expensive, because to getpredictable results the material had to be manufactured with greatprecision. Slight variations in the composition of the metal used orimpurities in the metal could result in wide variations in the work(force 1: distance) which the device is capable of doing. Consequentlythey have not gone into general use.

SUMMARY OF THE INVENTION A principal object of this invention is toprovide a tensile shock absorbing device which is simple and easy tomanufacture and one which in performance is much more predictable thanprior shock absorbers.

In accordance with this invention a precisely dimensioned wire which isalready available on the market has an accurately dimensioned metalliccoating formed thereon by means of a plating process, such a anelectrochemical plating process. The plated wire is drawn through apassage in a suitable anvil in which the passage closely confonns to thediameter of the uncoated wire. When an abnormal force in tension isapplied to the uncoated end of the wire, the coated portion of the wireis drawn through the anvil which results in stripping the coating fromthe wire and in so doing performs work which op poses the applied force.

Multiple strands can be used if higher tension loads are involved. Alsothe work that the absorber is capable of performing can be varied bychoice of wire diameter. Further the thickness of the plating can bevaried to obtain variations in work performance. It is also possible tovary the thickness of the coating along the length of the wire eitherunifonnly or in steps to obtain varying loads as the wire is drawnthrough the anvil.

Another object of this invention is to provide a tensile shock absorberof this type in which the core wire is of a high tensile strength metaland the integral coating is of a different metal "which has verydifferent characteristics from those of the wire.

A further object of this invention is the provision of a shock absorbingdevice having a coated wire in which the coating is applied without theuse of excessive heat which would alter the tensile characteristics ofthe wire.

A still further object of this invention is to provide a method ofmaking a tensile shock absorber in which a coating of frangible metal isapplied to a length of high tensile strength wire by an electrochemicalplating process to produce an integral structure.

A still further object of this invention is generally to improve theconstruction and performance of tensile shock absorbers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of atensile shock absorber of this invention;

FIG. 2 is an enlarged sectional view of the shock absorber of FIG. 1 inoperation;

FIGS. 3 and 4 are details of the core wire, showing modified coatings;and

FIG. 5 is a side elevation, partly in section, showing a sleeveassociated with the form of FIGS. 1 and 2 to prevent prematurepropagation of peeling.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the tensile shockabsorber of this invention in its normal position, ready to operate uponoccurrence of an abnormal shock load applied to wire 10 in the directionof the arrow. An unyielding linkage means, or fitting, 11 on the end ofwire 10 serves to connect the end of the wire to the member which it isdesired to decelerate upon a sudden, severe impact. Wire 10 extendsthrough a passage 12 in a fixed anvil l4 and may be of considerablelength to obtain long output displacements. For convenience it may bearranged in a coil 16 as shown in this figure.

Anvil 14 has an annular face 18 through the, center of which passage 12extends. This face 18 is usually slightly smaller in diameter than thediameter of a metallic coating 20 which is applied to a substantiallength of wire 10 above face 18.

In accordance with this invention, coating 20 is applied by a suitableelectrochemical plating process by which the desired thickness of thecoating can be deposited onto the wire very accurately and veryuniformly along its length as an integral part of the wire itself. Wire10 may be music, or piano, wire which has high tensile strength andaccurate diameter and is readily available in continuous length. Coating20 maybe nickel or chrome. When music wire is used with a nickelcoating, the nickel-sulfamate plating process gives good results and isrecommended. In this process the portion of the wire to be plated isimmersed in the chemical solution of the nickelsulfamate plating tankand as an electrical circuit is completed through the nickel and theassociated plating bath, nickel will be deposited upon the immersedportion of the wire. For a more complete description of thenickel-sulfamate plating process reference is made to Metals Handbook,8th Edition, Volume 2, Heat Treating, Cleaning and Finishing," publishedby American Society for Metals, pp. 432-433.

The advantage of applying coating 20 by electrochemical plating istwofold. It results in a coating which is integral with the wire and onewhich is accurate as to thickness along the entire length of the coatedportion of the wire. Also there is no danger of altering the tensilecharacteristics of the wire because it is essentially a cold process.Also, a much desired unifonnity of the plated-on metal itself resultswhich insures reliability of the results in operation. For applicationswhere a less stringent adherence of the plating is required, theimmersion or vacuum plating process could be utilized. The flame platingprocess provides good adherence, but is not preferred due to itstendency to alter the metal core characteristics.

The metal of the coating is frangible but if it is desired to get a moreaccurately controlled action a malleable metal such as copper can beadded. Music wire, which is steel, has a high tensile strength and isparticularly suitable for the purpose of this invention because it isreadily available in diameters from one-quarter inch to very fine wire.For use in such applications as vehicle seat restraints, the core wiremay be 0.047 inch in diameter, and the thickness of the coating may be0.010 inch of nickel or chrome, or chrome may be plated over nickel orcopper. Alloys such as zinc-copper, tin-cadmium, tin-lead, orcobalt-nickel may also be used. Music wire of 0.047 inch diameter has abreaking strength in tension of 477 pounds. Of course the peelingresistance of coating 20 should always be less than the tensile strengthof the core which insures that the wire will never break.

To prevent premature propagation of peeling of coating 20, anvil 14 mayhave an upstanding post 22 carrying a shelf 24 which is spaced above andoverlies the anvil face 18 and is provided with an aperture 26 which isaxially aligned with passage 12 and has a diameter equal to the coateddiameter of the wire.

In FIG. 3 a modifiedcoating 20a has been shown for-core wire in whichthe diameter of the coating is uniformly increased beginning at theuncoated portion'adjacent anvil face 18.

In FIG. 4 still another modified coating 20b has been shown for wire 10in which the diameter of the coating is increased by steps producinglands 30, 30a and 30b of increasing diameters. Either the FIG. 3 or theFIG. 4 construction can be easily produced by the electrochemicalplating process, by a continuous and gradual withdrawal of the wire fromthe plating bath in the case of FIG. 3 and by an intermittentstep-by-step withdrawal in the case of FIG. 4.

OPERATION Normally the uncoated portion of wire 10 is drawn throughpassage 12 in anvil 14 so the coated portion 20 of the wire rests uponanvil face 18 as shown in FIG. 1. Fitting lll is then attached to theend of the wire 10 by means of which the seat restraining belt or otherdevice is attached. If a tension force is applied to wire 10 in thedirection of the arrow in FIG. 1 which exceeds the designed resistanceof coating 20, the coating will peel progressively from the wire asillustrated in FIG. 2. In this figure peeling of the coating isillustrated as a progressive fracture of the coating which will be thecase if a frangible metal such as nickel or chromium is used for coating20. If a malleable metal such as copper is used, a uniform rate peelingwill take place without intermittent fracture of the coating material.In any case, the core wire 10 is never deformed in any way during theoperation of this shock absorber.

If the nature of the coating 20 is suchthat the propagation of thepeeling action extends too far above the face 18 of anvil l4, shelf 24shown in FIG. 3 can be provided which establishes a limited peeling zonebetween the anvil face and the bottom surface of the shelf which resultsin a steady work load for the device during the entire operation. Thisshelf feature is only applicable to the FIGS. l and 2 form in which thecoating 20 is of uniform diameter along the length of the wire.

An important feature of this invention resides in the face that the corewire 10 is not excessively heated in the plating process nor is it everin operation deformed in any way. The only metal which undergoesdeformation is the plated-on coating. Since this coating is applied byelectrochemical plating process it can be very accurately controlledentirely independently of the characteristics of core wire 10.

It will be evident that, while wire of round cross-section has beenshown and referred to throughout as the tension member of the shockabsorber, the core section can have any desired cross section, althoughround wire is preferred since its diameter can be closely controlledwith ease as well as the diameters of the passages 12 and 26.

I wish it to be understood that I do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

lclaim:

l. A tensile shock absorber including a metal wire of high tensilestrength having an integral metallic coating on a portion of its length,an anvil having a passage therethrough which conforms in diameter to thediameter of the uncoated wire and through which the uncoated portion ofthe wire can be freely drawn, and a fitting secured to the uncoated endof said wire for attachment of a device to be decelerated upon suddenimpact.

2. The shock absorber of claim 1 in which the coating on the metal wireis a frangible metal.

3. The shock absorber of claim 1 in which the coating on the metal wireis applied by an electrochemical plating process.

4. The shock absorber of claim 1 in which the high tensile wire is musicwire and the coating is nickel applied by the nickel-sulfamate platingprocess.

5. The shock absorber of claim 1 in which a fixed sleeve is located inspaced relation to the anvil having a passage therethrough whichconforms closely to the diameter of the wire coating.

6. A tensile shock absorber including a metal wire of high tensilestrength, a coating of frangible metal applied to a portion of said wireby an electrochemical plating process, an anvil having a face and apassage extending from said face through said anvil which closelyconforms in diameter to the diameter of the uncoated portion of saidwire and through which said wire extends with the coated portion of saidwire abutting the face of said anvil, and a fitting attached to the endof said uncoated portion on the side of said anvil remote from saidface.

7. The shock absorber of claim 6 in which the frangible coating isnickel and the metal wire is high tension steel wire.

8. The shock absorber of claim 6 in which the anvil face is circular andhas a diameter smaller than the diameter of the coating on said wire.

9. The shock absorber of claim 6 in which the anvil has an upstandingsupport at one side of the wire passage therethrough which carries ashelf which extends over said passage in spaced relation to said anviland itself has a passage axially aligned with the passage in said anvil,the passage in said shelf having a diameterwhich closely conforms to thediameter of the coated wire.

10. In a frangible tension shock absorber, an elongated nondeformablemetallic core member having a uniform diameter throughout its length, ananvil having a face of limited area, means for passing said core memberthrough said anvil including a passage extending from said face throughsaid anvil, an attachment type fitting secured to the free end of saidcore member by which the latter can be drawn through said anvil, andmeans for normally securing said core member against such passage andyielding only upon sudden impact comprising an annular plated-on coatingof frangible metal on said member, one end of which rests upon saidface.

11. The shock absorber of claim 10 in which the face of the anvil isannular and has a diameter less than the diameter of said coating.

12. In a frangible tension shock absorber, a nondefonnable hardenedsteel wire of substantial length having a uniform diameter throughoutits length, an anvil having an annular face of limited area, means forpassing said wire freely through said anvil including a passageextending from said face through said anvil, said passage having thesame diameter as said wire, an attachment type fitting secured to thefree end of said wire on the side of said anvil remote from said face bywhich the wire can be drawn through said anvil, and means for i normallysecuring said wire against such passage and yielding only upon suddenimpact comprising an annular metallic coating of nickel on said wire,one end of which rests upon and overlies said face.

13. The shock absorber of claim 12 in which the anvil has an uprightframe including a shelf which overlies the face of the anvil and isspaced above said face, said shelf having a passage therethrough whichis aligned with the passage through said anvil and said shelf passagehaving a diameter substantially equal to the diameter of the plated wireand through which the latter can pass freely.

14. In a frangible tension shock absorber, a nondeformable high tensioncore wire of uniform diameter throughout its length having an integralmetallic plated-on coating on a portion of its length, the thickness ofsaid coating being progressively increased along the coated portion ofsaid wire, an anvil having a face, means for passing the uncoatedportion of said wire freely through said anvil comprising a passageextending from said anvil face through said anvil, said passage having adiameter equal to the diameter of said core wire, and an at-

1. A tensile shock absorber including a metal wire of high tensilestrength having an integral metallic coating on a portion of its length,an anvil having a passage therethrough which conforms in diameter to thediameter of the uncoated wire and through which the uncoated portion ofthe wire can be freely drawn, and a fitting secured to the uncoated endof said wire for attachment of a device to be decelerated upon suddenimpact.
 2. The shock absorber of claim 1 in which the coating on themetal wire is a frangible metal.
 3. The shock absorber of claim 1 inwhich the coating on the metal wire is applied by an electrochemicalplating process.
 4. The shock absorber of claim 1 in which the hightensile wire is music wire and the coating is nickel applied by thenickel-sulfamate plating process.
 5. The shock absorber of claim 1 inwhich a fixed sleeve is located in spaced relation to the anvil having apassage therethrough which conforms closely to the diameter of the wirecoating.
 6. A tensile shock absorber including a metal wire of hightensile strength, a coating of frangible metal applied to a portion ofsaid wire by an electrochemical plating process, an anvil having a faceand a passage extending from said face through said anvil which closelyconforms in diameter to the diameter of the uncoated portion of saidwire and through which said wire extends with the coated portion of saidwire abutting the face of said anvil, and a fitting attached to the endof said uncoated portion on the side of said anvil remote from saidface.
 7. The shock absorber of claim 6 in which the frangible coating isnickel and the metal wire is high tension steel wire.
 8. The shockabsorber of claim 6 in which the anvil face is circular and has adiameter smaller than the diameter of the coating on said wire.
 9. Theshock absorber of claim 6 in which the anvil has an upstanding supportat one side of the wire passage therethrough which carries a shelf whichextends over said passage in spaced relation to said anvil and itselfhas a passage axially aligned with the passage in said anvil, thepassage in said shelf having a diameter which closely conforms to thediameter of the coated wire.
 10. In a frangible tension shock absorber,an elongated nondeformable metallic core member having a uniformdiameter throughout its length, an anvil having a face of limited area,means for passing said core member through said anvil including apassage extending from said face through said anvil, an attachment typefitting secured to the free end of said core member by which the lattercan be drawn through said anvil, and means for normally securing saidcore member against such passage and yielding only upon sudden impactcomprising an annular plated-on coating of frangible metal on saidmember, one end of which rests upon said face.
 11. The shock absorber ofclaim 10 in wHich the face of the anvil is annular and has a diameterless than the diameter of said coating.
 12. In a frangible tension shockabsorber, a nondeformable hardened steel wire of substantial lengthhaving a uniform diameter throughout its length, an anvil having anannular face of limited area, means for passing said wire freely throughsaid anvil including a passage extending from said face through saidanvil, said passage having the same diameter as said wire, an attachmenttype fitting secured to the free end of said wire on the side of saidanvil remote from said face by which the wire can be drawn through saidanvil, and means for normally securing said wire against such passageand yielding only upon sudden impact comprising an annular metalliccoating of nickel on said wire, one end of which rests upon and overliessaid face.
 13. The shock absorber of claim 12 in which the anvil has anupright frame including a shelf which overlies the face of the anvil andis spaced above said face, said shelf having a passage therethroughwhich is aligned with the passage through said anvil and said shelfpassage having a diameter substantially equal to the diameter of theplated wire and through which the latter can pass freely.
 14. In afrangible tension shock absorber, a nondeformable high tension core wireof uniform diameter throughout its length having an integral metallicplated-on coating on a portion of its length, the thickness of saidcoating being progressively increased along the coated portion of saidwire, an anvil having a face, means for passing the uncoated portion ofsaid wire freely through said anvil comprising a passage extending fromsaid anvil face through said anvil, said passage having a diameter equalto the diameter of said core wire, and an attachment type fittingsecured to the uncoated free end of said core wire for attachment of adevice to be decelerated upon sudden impact.
 15. The shock absorber ofclaim 14 in which the thickness of the metallic coating on the core wireis increased uniformly along the coated portion of the wire.
 16. Theshock absorber of claim 14 in which the thickness of the metalliccoating is increased by a series of steps producing lands ofprogressively increasing diameter.